深海底鉱物資源の製錬におけるバイオリーチングの応用

抄録

Because of the depletion of terrestrial mineral resources, the recovery of base and precious metals from deep-sea mineral resources is sure to become of significant importance. Although pyro- and hydrometallurgical processes have been developed to recover valuable metals from deep-seabed ferromanganese mineral resources, another possibility is the application of biohydrometallurgical processes. The use of microorganisms to facilitate the extraction of metals from minerals is referred to as "bioleaching" which is an economical and environmentally friendly process. The bioleaching of terrestrial sulfide minerals has developed into a successful and expanding area of biotechnology: commercial heap bioleaching is typically used for low-grade sulfide ores of 0.5% or less Cu, and commercial tank bioleaching is used mostly in the pretreatment of gold ores. The bioleaching technologies can be applied to metal extraction from deep-sea hydrothermal sulfides as well as terrestrial sulfide minerals. However, little attention has been given to the bioleaching of oxide minerals such as ferromanganese crusts and nodules. A new bioleaching system has been more recently proposed for ferromanganese crusts and nodules, in which dissolved Fe (II) is microbially produced by the Fe (III) -reducing bacterium and simultaneously used to extract Co, Ni and Mn under anaerobic conditions. The proposed bioleaching is a potentially attractive method, with good metal extractions taking only 7 hours of batch operation at room temperature and neutral pH. Further research should be planned to clarify the bioleaching behavior of other elements such as rare earths, Ti and Mo from deep-sea ferromanganese crusts. It can be concluded that bioleaching is an attractive processing route to recover valuable metals from deep-seabed mineral resources.